摘要
在核桃破壳加工中,壳体尾部倒刺是导致碎仁和“露白”现象的主要原因。为此,提出破壳前切除尾部的结构预处理方法,先切除核桃尾部并破坏分心木结构,打破壳仁间的有机连接,随后实施冲击破壳。落锤冲击试验表明,该预处理能够有效降低冲击载荷对果仁的损伤,并减少“露白”风险,从而实现核仁与分心木隔膜的完整获取。为深入探究切尾核桃的冲击破碎机理,采用结合内聚力单元(Cohesive Element,CIE)的有限耦合离散单元方法(FDEM),对简化后的切尾核桃球壳模型的冲击破碎特性进行了数值模拟分析,根据核桃壳的碎裂程度可将破碎结果划分为未破碎、局部坍塌、破碎和粉碎4种典型类型。研究结果表明,在0°冲击条件下,模式间临界转变速度分别为2.5 m/s(未破碎至局部坍塌)、12 m/s(局部坍塌至破碎)和85 m/s(破碎至粉碎);此外,当冲击速度小于10 m/s时,损伤比随冲击角度增加呈线性下降,大于10 m/s时则呈指数下降,表明增大冲击角度可显著抑制破碎程度。研究结果可为新型核桃破壳机械的设计、关键参数优化和工艺调控,以及其他坚果的破碎特性研究提供理论基础。
In walnut shell breaking processing,the caudal barb of the shell is the primary cause of kernel fragmentation and kernel exposure.To address this issue,a structural pre-treatment method that removes the caudal barb prior to shell breaking was proposed.This method first cuts off the walnut′s caudal barb and disrupts the chalaza structure,thereby breaking the organic connection between the shell and kernel,followed by impact shelling.Drop-weight impact tests demonstrated that this pre-treatment can effectively reduce the impact load damage to the kernel and lower the risk of kernel exposure,thus achieving intact separation of the kernel and Diaphragma juglandis Fructus.To further investigate the impact fragmentation mechanisms of cutting tail walnuts,a numerical simulation analysis was conducted on a simplified tipped walnut spherical shell model using a coupled Finite-Discrete Element Method(FDEM)incorporating Cohesive Elements(CIE)to characterize its impact fragmentation behavior.The research results indicated that the fragmentation outcomes of the walnut shell can be classified into four typical types based on the degree of fragmentation:unbroken,local collapse,fragmentation,and shattering.Under a 0°impact condition,the critical transition velocitied between modes were 2.5 m/s(unbroken to local collapse),12 m/s(local collapse to fragmentation),and 85 m/s(fragmented to shattering).Furthermore,increasing the impact angle significantly inhibits the degree of fragmentation.When the impact velocity was<10 m/s,the damage ratio decreased linearly with increasing impact angle,whereas when the impact velocity was>10 m/s,it decreased exponentially.The findings of this study can provide an important reference for the design of novel walnut shelling machinery,the optimization of key parameters and process control,and also can offer a theoretical basis for research on the fragmentation characteristics of other nuts.
作者
王曈
张宏
陈沛瑀
兰海鹏
Wang Tong;Zhang Hong;Chen Peiyu;Lan Haipeng(College of Mechanical and Electronic Engineering,Tarim University,Alar 843300,China)
出处
《农机化研究》
北大核心
2026年第7期159-167,共9页
Journal of Agricultural Mechanization Research
基金
国家自然科学基金项目(12462017,32560427)。
关键词
切尾核桃
尾部倒刺
分心木隔膜
FDEM
冲击破碎
cutting tail walnut
caudal barb
Diaphragma juglandis Fructus
FDEM
impact breakage
